Merge branch 'master' into astropy

This brings in all changes to trunk for PyFITS v3.3.0 between
8d2a54d3ef93e356a0d20a71924cff7ab8c87426 (SVN r2391) and
2ab1b36e8135beb37bcc53859985a52a82a0d880 (SVN r2796).  These are all the
changes from that period that were not also ported as bugfixes to the
3.2.x branch.

Conflicts:
	.coveragerc
	.travis.yml
	README.txt
	astropy/io/fits/card.py
	astropy/io/fits/column.py
	astropy/io/fits/core.py
	astropy/io/fits/fitsrec.py
	astropy/io/fits/hdu/base.py
	astropy/io/fits/hdu/compressed.py
	astropy/io/fits/header.py
	astropy/io/fits/tests/test_diff.py
	astropy/io/fits/tests/test_header.py
	astropy/io/fits/tests/test_image.py
	astropy/io/fits/tests/test_table.py
	astropy/io/fits/util.py
	docs/io/fits/appendix/header_transition.rst
	docs/io/fits/appendix/history.rst
	docs/io/fits/users_guide/users_headers.rst
	docs/io/fits/users_guide/users_tutorial.rst
	docs/io/fits/users_guide/users_verification.rst
	docs/source/conf.py
	docs/source/developers_guide/developers_guide.rst
	lib/pyfits/_release.py
	lib/pyfits/tests/test_checksum.py
	setup.cfg
	setup.py
	tox.ini

Conflicts:

	astropy/io/fits/__init__.py
	astropy/io/fits/card.py
	astropy/io/fits/column.py
	astropy/io/fits/convenience.py
	astropy/io/fits/core.py
	astropy/io/fits/diff.py
	astropy/io/fits/file.py
	astropy/io/fits/fitsrec.py
	astropy/io/fits/hdu/__init__.py
	astropy/io/fits/hdu/base.py
	astropy/io/fits/hdu/compressed.py
	astropy/io/fits/hdu/groups.py
	astropy/io/fits/hdu/hdulist.py
	astropy/io/fits/hdu/image.py
	astropy/io/fits/hdu/nonstandard.py
	astropy/io/fits/hdu/streaming.py
	astropy/io/fits/hdu/table.py
	astropy/io/fits/header.py
	astropy/io/fits/py3compat.py
	astropy/io/fits/scripts/fitscheck.py
	astropy/io/fits/scripts/fitsdiff.py
	astropy/io/fits/tests/test_checksum.py
	astropy/io/fits/tests/test_core.py
	astropy/io/fits/tests/test_diff.py
	astropy/io/fits/tests/test_division.py
	astropy/io/fits/tests/test_groups.py
	astropy/io/fits/tests/test_hdulist.py
	astropy/io/fits/tests/test_header.py
	astropy/io/fits/tests/test_image.py
	astropy/io/fits/tests/test_nonstandard.py
	astropy/io/fits/tests/test_structured.py
	astropy/io/fits/tests/test_table.py
	astropy/io/fits/tests/test_uint.py
	astropy/io/fits/tests/test_util.py
	astropy/io/fits/tests/util.py
	astropy/io/fits/util.py
	astropy/io/fits/verify.py
	docs/io/fits/api/hdus.rst
	docs/io/fits/usage/headers.rst
	docs/io/fits/usage/table.rst
	docs/io/fits/usage/unfamiliar.rst
	docs/io/fits/usage/verification.rst
	docs/io/fits/users_guide/users_tutorial.rst
Fix a couple unused imports and small typos that were brought in along with the merge
Fixed stray reference to the pyfits module in this docstring
Fix references to pyfits in this example as reported in #2303
Fix reference to PyFITS [skip ci]
Merge in fix for https://github.com/astropy/astropy/issues/2595
from https://github.com/spacetelescope/PyFITS/issues/69